This is not a simple question, although it appears to be so. A simple, answer, however, acknowledges the complexity while recognizing that Geertz’s focus on systems of symbols, “pervasive, long lasting moods and motivations” and “aura of facticity” were used by Douglas J. Davies in his the Mormon Culture of Salvation to great effect.

Yes, Geertz’s definition can fit Mormonism.

However, a more critical look at the definition, that takes into account problems with the notion of symbols and their formation, power, the difficulty of system, breaks in pervasiveness, and problems with perceptions of facticity as are also found in anthropological work, can also be used to make sense of Mormonism.

The question, however, asks if it is a religious system according to Geertz. Well, that is more difficult because Geertz is focusing on system as defining religion and not religion as defining system. Mormonism has system and it functions as a religion. Despite the analytical concerns here, I would still argue that Geertz’s definition productively fits Mormonism.

Douglas J. Davies also wrote in to recommend that you read his book in which he engages this question at length: